Method of and apparatus for scoring a coated substrate

ABSTRACT

An automotive window is manufactured by silk screening a pattern of a ceramic paste on a piece of glass having peripheral dimensions greater than the peripheral dimensions of the window. During the silk screening, portions of the screen extending beyond the pattern are supported by glass portions extending beyond the window to prevent bending of the screen near the pattern. The piece is scored through the pattern to define the window or a window blank within the piece and thereafter the glass around the window is removed. The window is then tempered at which time the ceramic paste fuses to the window.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

This invention relates to a method of and apparatus for scoring a coatedsubstrate e.g. an automotive window blank.

2. Discussion of the Technical Problems:

Automotive body weight and wind resistance are being reduced to improvefuel efficiency. One technique is to eliminate metal trim around theautomotive windows or lites by flush glazing. In flush glazing the liteis secured in a recess by an adhesive. To prevent degradation of theadhesive as a result of exposure to the sun's rays, an opaque endlessband is provided around the marginal edge portions of the lite. The bandpreferably extends to the peripheral edge of the lite; has a widthsufficient to shade the underlying adhesive; has a width sufficientlynarrow to provide maximum vision and is abrasive resistant to withstandcleaning and the elements. These requirements have been achieved by silkscreening a band of a ceramic paste on an automotive window blank andfusing the paste to the glass by heat. In order to assure shading of theunderlying adhesive and extending the pattern out to the peripheraledge, the silk screen pattern is slightly larger than the blank. Thistechnique although accomplishing the above results reduces the useablelife of the screen because the screen bends over the cut glass edgeduring the silk screening process.

It would be advantageous, therefore, to provide a silk screeningtechnique to manufacture automotive lites for flush glazing that doesnot have the limitations of the above-described techniques.

SUMMARY OF THE INVENTION

This invention relates to a method of manufacturing a sheet ofrefractory material e.g. an automotive window having a predeterminedconfiguration and a pattern e.g. an endless band of a fired ceramic orenamel on or adjacent the marginal edge portions of the window. Themethod includes the steps of coating the pattern e.g. silk screening aceramic paste within edges of a glass piece with selected portions ofthe coating e.g. the endless band of ceramic paste defining the sheetwithin the piece. Thereafter the piece is scored e.g. through theendless band of enamel paste to outline the sheet within the pieceafterwhich the sheet is removed from the piece.

In the practice of the invention the useable life of silk screens isincreased because the portion of the silk screen outside of the patternis supported by portions of the piece extending beyond the sheet.

Further, this invention relates to an apparatus for scoring a sheet ofrefractory material having a coating thereon, e.g. a baked enamel paste.The apparatus has a wiper to clear a score path through the paste and ascoring wheel upstream of the wiper for scoring the sheet along thescore path.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a flow diagram illustrating steps incorporating features ofthe invention for manufacturing an automotive window;

FIG. 2 is an isometric view showing the scoring of a coated automotivewindow blank in accordance with the teachings of the invention;

FIG. 3 is a front elevated view of an automotive window manufactured inaccordance with the teachings of the invention;

FIG. 4 is an isometric view illustrating the silk screening of a ceramicpaste pattern on a glass sheet in accordance with the teachings of theinvention;

FIG. 5 is a side elevated view showing the application of bending momentforces about a score to remove trim from an automotive blank inaccordance with the teachings of the invention;

FIG. 6 is a side elevated view illustrating the edging of an automotiveblank cut edge in accordance with the teachings of the invention;

FIG. 7 is a side elevated view of a scoring apparatus for scoring abaked enamel paste pattern in accordance with the teachings of theinvention; and

FIG. 8 is a plan view of FIG. 7.

DESCRIPTION OF THE INVENTION

The flow chart shown in FIG. 1 illustrates process steps incorporatingfeatures of the invention for the production of automotive windows orlites, e.g. automotive back windows. As will be appreciated, theinvention is not limited to the manufacture of automotive back windowswhich is presented to illustrate one environment in which the inventionmay be practiced. A glass sheet or substrate 10 (see FIG. 2) havingperipheral dimensions larger than corresponding peripheral dimensions ofthe finished back window 12 (see FIG. 3) has a pattern 14 of a ceramicor enamel paste conveniently applied thereto e.g. by silk screening.Taught in U.S. Pat. No. 3,638,564 is a silk screen technique that is notlimiting to the invention but may be used in the practice of theinvention. The teachings of U.S. Pat. No. 3,638,564 are herebyincorporated by reference. During the silk screening, sheet surfaceportions or trim 16 which extend beyond area 18 of the back window blank20 (FIG. 2) support silk screen portions 22 beyond screen pattern 24(FIG. 4) corresponding to the pattern 14 on the sheet 10 (FIG. 2). Inthis manner bending of the screen portions 22 over cut glass edges iseliminated to increase the life of the screen.

As illustrated in the flow chart of FIG. 1, in one embodiment the glasssheet 10 having the ceramic paste pattern 14 is conveniently scored asshown in FIG. 2 through the pattern 14 to define the automotive blank 20surrounded by the screen supporting surface portions 16. During thescoring of the substrate 10, the paste of the pattern 14 acts as alubricant to minimize surface defects. Preferably the score 26 extendsthrough the tension zone of the glass sheet with minimal, if any,surface defects to minimize or retard healing or closing of the score.If the score does heal, removal of the supporting portions 16 from thewindow blank 18 may require rescoring of the sheet 10.

It is generally recognized that a glass sheet has an inner tension zonebetween two outer compression zones. The tension zone has a depthapproximately 60 percent of the glass thickness and each of thecompression zones has a depth approximately 20 percent of the glassthickness. A technique known as deep fissure scoring provides a scorehaving minimal surface damage. In general, an initial score has a depthdown to the compression zone of the glass sheet and thereafter interactswith the tension zone to propagate the score to the opposite compressionzone. This type of score is taught in U.S. Pat. No. 3,756,482 whichteachings are hereby incorporated by reference. As shown in FIG. 2,relief scores 28 extending from peripheral edge portions of the sheet 10to the score 26 are imposed in the sheet 10 for ease of removing thesupporting sheet portions 16 in subsequent operations to be discussedbelow.

As shown in FIG. 1, after the sheet 10 is scored, the ceramic pastepattern is preferably heated or baked at low temperatures to slowlyremove any volatiles therein. Although not shown in the flow chart ofFIG. 1, the supporting sheet portions 16 may be conveniently removedfrom the window blank 20 prior to baking of the ceramic paste pattern14. To prevent possible damage to the pattern 14 and to take advantageof the heat of the baking step which may propagate the scores 26 and 28through the sheet 10, it is recommended that the baking operation beperformed prior to removal of the supporting sheet portions 16. Afterbaking, the supporting sheet portions 16 remaining about the windowblank 20 are removed in any convenient manner. For example and as shownin FIG. 5, downward forces 30 are applied about the baked ceramic pastepattern 14 as an upward force 32 is applied on the opposite side at thescore 28 or 26.

The window blank 20 having the baked ceramic paste pattern 14 may betempered, e.g. as taught in U.S. Pat. No. 4,119,426 which teachings arehereby incorporated by reference, or processed through an edgingoperation as shown in FIG. 6 to remove damage at the cut edges 36. Thismay be accomplished by using a hand held belt sander 38 which is aconventional operation and does not require further discussion. Afteredging the window blank 20 may be tempered to provide the automotivewindow 18 shown in FIG. 3. It should be noted that extreme edge damagemay cause the glass window to fracture during the tempering operationand therefore should be removed. However, it has been found that moreedge damage can be tolerated during tempering without glass breakagewhen the window blank 20 has an opaque coating at the edge. It istheorized that the opaque coating concentrates and retains heat at themarginal edge portions of the glass which slows cooling at the heatedmarginal edge portions.

Referring back to FIG. 1, in another embodiment of the invention, afterthe ceramic paste pattern 14 has been silk screened on the sheet 10, thesheet 10 is baked as previously discussed to remove the volatilestherein. Thereafter, the sheet 10 is scored to define the automotiveblank 20 having the supporting portions 16. Shown in FIGS. 7 and 8 isscoring apparatus 50 incorporating features of the invention that may beused for scoring a pattern of a highly viscous coating, e.g. a bakedceramic paste. The scoring apparatus 50 has a housing 52 mounted on stem54 of a force applying device 56, e.g. of the type taught in U.S. Pat.No. 4,137,803 which teachings are hereby incorporated by reference.Scoring wheel 58 is rotatably mounted in the housing 52 on shaft 60upstream of wiper 62 as the scoring apparatus 50 conveniently moves inthe direction of the arrow 64. Wiper end 64 clears a path through thebaked enamel paste pattern 14 as the scoring wheel 58 scores the glasssheet 10. It is recommended that the wheel 58 and wiper end 64 be closeto one another to provide a clear scoring path for non-linear scorese.g. around bends.

After the scoring, the trim or supporting sheet surface portions 16 areremoved and the tempering or edging steps previously discussed areperformed.

As can now be appreciated, the invention is not limited to the scoringof glass sheets which are subsequently tempered, e.g. the invention maybe practiced on automotive windshields. Further, if the glass sheet isto be bent, the baking of the ceramic paste pattern to remove thevolatiles may be practiced during the bending of the sheet. Further, theinvention is not limited to the composition of the ceramic paste. Stillfurther, the technique for eliminating or reducing edging of theautomotive window blank to be tempered may be used on glass sheets to betempered for architectural glazing.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a glass sheet 10 having a thickness of about3/16 inch (0.47 centimeters), a length of about 3 feet (0.9 meters) anda width of about 5 feet (1.5 meters) has a trapezoidal pattern 14 of aceramic paste of the type sold by Drakenfield Co. of Washington, Pa.,24-1169 mat black silk screened on sheet surface 16 in any convenientmanner. The base of the pattern has a length of about 4 feet (1.2meters) with the opposite side having a length of about 3 feet (0.9meters). The sides each have a length of about 1 1/2 feet (0.45 meters).Score 26 imposed in the glass sheet through the pattern and between thesides to define automotive blank 20 having supporting glass portions 16as shown in FIG. 2. The score 26 is imposed in the sheet 10 supported ontable 70 by a scoring wheel 72 having a 7/32 inch diameter, an apexangle of about 140°- 155°, urged against the sheet under a force ofabout 15-25 pounds (6.8-11.4 kilograms) and moving relative to the sheetat a speed of about 10-30 inches (0.25-0.75 meters) per second. Theinitial score in the sheet is approximately 30 percent of the glassthickness and interacts with the inner tension zone to propagate thescore through the tension zone to the opposite compression zone. Afterthe glass sheet is scored, it is conveniently baked at a temperature ofabout 400° F. (204° C.) to drive out the volatiles e.g. pine oil in theceramic paste. After the baking, bending moments 30 and 32 are shown inFIG. 5 are conveniently applied at glass surface 34 about the scores 26and 28 to remove the sheet portions 16 not removed during the bakingoperation. The edges of the glass sheet are thereafter edged in anyconvenient manner e.g. by a hand sander 38 as shown in FIG. 6 andthereafter the window blank 20 is tempered in any convenient manner toprovide the automotive back window 12 shown in FIG. 3.

In another embodiment of the invention the glass sheet 10 is baked asdiscussed above after the ceramic paste pattern 14 is silk screenedthereon. With reference to FIGS. 7 and 8 a scoring apparatus 50 having ascoring wheel 58 similar to the scoring wheel 72 discussed above ismounted in housing 52 in spaced relation to a spring loaded wiper 62 ofthe type sold by Vlier Engineering Corp. as spring plunger No. S-52N.The wiper 62 has an upper threaded portion 74 threaded in the housing 52and a lower spherical end 64. The spherical end 64 is spaced about 1/4inch (0.64 centimeter) from the wheel 58 and spaced about 0.001 inch(0.025 millimeter) above the glass sheet surface 16. As the scoringapparatus 50 moves in the direction of the arrow 64 at a speed of about10-30 inches (0.25-0.75 meters) per minute, the spherical end portion 64clears a path for the scoring wheel 58. After the sheet is scored, thesupporting glass portions 16 are removed as previously discussed and theblank 20 is edged and tempered as previously discussed. During thetempering operation, the ceramic paste fuses to the glass.

As can now be appreciated, the above examples are not limited to theinvention and are presented to illustrate the practice of the inventionin the manufacture of automotive windows. Further, in the discussion theterms "automotive window blank" and "automotive window" were used forclarity of discussion and therefore the automotive window may be theautomotive window blank and vice versa.

What is claimed is:
 1. A method of manufacturing a sheet of refractorymaterial having a predetermined configuration and having a pattern on asurface of the sheet with at least a portion of the pattern at themarginal edge of the sheet, comprising the steps of:silk screening aceramic paste pattern within edges of a piece of refractory materialhaving peripheral dimensions greater than the peripheral dimensions ofthe sheet so as to support at least a screen portion which extendsbeyond the ceramic paste pattern by portions of the refractory piecethat extend beyond the peripheral dimensions of the sheet; scoring therefractory piece to define the sheet within the piece, said scoring stepincluding scoring through the ceramic paste pattern to be at themarginal edges of the sheet; and removing the sheet from the piece. 2.The method as set forth in claim 1 wherein the ceramic paste patternincludes an endless band at the marginal edge portions of the sheet. 3.The method as set forth in claims 1 or 2 wherein the paste has volatilesand further including the step of heating the sheet having the ceramicpaste pattern thereon to remove the volatiles in the ceramic pastepattern.
 4. The method as set forth in claim 3 wherein said scoring stepis practiced after said heating step.
 5. The method as set forth inclaim 3 wherein said scoring step is practiced before said heating step.6. The method according to claim 3 wherein the piece of refractorymaterial is a glass piece and the sheet is an automotive window blank.7. The method as set forth in claim 6 wherein the scored piece is anautomotive window blank having supporting glass surface portions andsaid scoring step is practiced after said heating step and furtherincluding a step of:tempering the window blank wherein the ceramic pastepattern during said tempering step fuses to the automotive blank toprovide the automotive window.
 8. The method as set forth in claim 7further including a step ofedging portions of the automotive blank edgeprior to practicing said tempering step.
 9. The method as set forth inclaim 6 wherein said scoring step is practiced after said heating stepand further includes:clearing a scoring path through the ceramic pastepattern overlying portions of the sheet to be scored.
 10. The method asset forth in claim 9 wherein the scored piece is an automotive windowblank having supporting glass surface portions and further including astep of:tempering the automotive blank wherein the ceramic paste patternduring said tempering step fuses to the automotive blank to provide theautomotive window.
 11. The method as set forth in claim 10 furtherincluding a step of:edging portions of the automotive blank edge priorto practicing said tempering step.
 12. The method as set forth in claim6 wherein the scored piece is an automotive window blank havingsupporting glass surface portions and further including a stepof:tempering the automotive blank wherein the ceramic paste patternduring said tempering step fuses to the automotive blank to provide theautomotive window.
 13. The method as set forth in claim 12 furtherincluding a step of:edging portions of the automotive blank edge priorto practicing said tempering step.
 14. The method as set forth in claim1 or 2 further including a step of heating the sheet to fuse the ceramicpattern to the sheet.
 15. The method as set forth in claim 14 whereinthe sheet is a glass sheet of a laminated automotive windshield.
 16. Amethod of tempering a glass sheet, comprising the steps of:silkscreening a heat absorbing ceramic paste pattern on a piece of glass todefine a glass sheet to be tempered, said silk screening step beingpracticed while supporting screen portions extending beyond the screenpattern by trim which extends beyond the heat absorbing pattern on theglass piece; removing the trim to provide the glass sheet to betempered, the glass sheet having as removed peripheral and marginaledges and heat absorbing material on the marginal edge of at least onesurface of the sheet; and tempering the glass sheet having the asremoved edges and heat absorbing material on the marginal edge of thesheet surface.
 17. The method as set forth in claim 16 wherein thepattern includes an endless band of ceramic paste applied to themarginal edge of the sheet.
 18. The method as set forth in claim 17wherein the heat absorbing pattern is a ceramic paste having volatilesand further including a step of heating the sheet having the heatabsorbing pattern thereon to remove the volatiles in the paste.
 19. Themethod as set forth in claim 18 wherein said removing step includesscoring the piece and said scoring step is practiced after said heatingstep.
 20. The method as set forth in claim 18 wherein said removing stepincludes scoring the piece and said scoring step is practiced beforesaid heating step.
 21. The method as set forth in claim 18 wherein thesheet is an automotive window.
 22. The method as set forth in claim 21wherein said removing step includes scoring the sheet and said scoringstep is practiced after said heating step and further includes a stepof:clearing a scoring path through the ceramic paste pattern overlyingportions of the piece to be scored.